The present invention relates, in general, to a method for strictly managing group membership in Internet multicast applications and, more particularly, to a method for strictly managing group membership in Internet multicast applications, capable of strictly managing group membership without revising the existing multicast applications by partially extending a session description protocol and providing a group management protocol that is able to perform a group management function.
In a multicast application in which security is required and only specified users of a group may participate, the management of the participants of the group should be strictly performed. In particular, in a procedure, such as an Internet poll, precise participant information at a certain point of time is very important. Incidentally, although in the same multicast application, a case occurs in which a loosely managed group session is needed and a case also occurs in which a strictly managed group session is needed, as occasion demands.
As well known to those skilled in the art, conventional multicast applications are performed by means of protocols including an Internet Group Management Protocol (IGMP), a Session Description Protocol (SDP), a Session Announcement Protocol (SAP), a Session Initiation Protocol (SIP) and a multicast routing.
Using the IGMP, participants join a corresponding group address of a multicast router. Information, such as an encryption type of a multicast session, connection information, a session title, a connection point, etc. may be described in the form of text by means of the SDP. When the described contents are sent to a well-known multicast group address using the SAP, a SAP message sent by a sender arrives at all multicast routers, in which all joined users exist, along a multicast routing route and the participants of the group may find the message. The SIP serves to allow the creation of a new multicast session and the release of the multicast session, to invite non-participating users to join the group, and to make location information on session participants known.
In such a case, since no provision is made for limiting the qualification for joining in the multicast router, all persons who know a group address may participate. Additionally, there is a problem in which the multicast router, in which the IGMP is utilized, does not manage the information on who joins a certain address, but confirms whether a joiner exist or not regardless of the number of joiners. As a consequence, according to the conventional art, the strict management of the participants of a group is almost impossible because the participants of the group are managed loosely in the art.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a method for managing group membership in Internet multicast applications, capable of strictly managing group membership without revising the existing multicast applications by partially extending SDP and providing GMP that is able to perform a group management function.
In order to accomplish the above object, the present invention provides a method for strictly managing group membership in Internet multicast applications, comprising a group creation and enrollment step in which a group management server creates a group and performs group registration as a group management client requests a group registration by creating group information and transmitting the information to the group management when request for multicast group creation occurs; a group announcement step in which the group management server announces the created group using a multicast group address; a group query step in which the group management client which knows a group ID inquires the group information of the group management server and acquires a response; a group information acquisition step in which the group management client which does not know a group ID joins a known group address and acquires the group information that arrives at the known group address; a group registration step in which the group management client enrolls in the group management server as a participant; a group leaving step in which the group management client leaves the group by transmitting information for leaving the group to the group management server; a failure information response step in which the group management server transmits information on a reason for failure to the group management client when the group management server fails in processing a request for group creation, query, enrollment or leaving; and a fragment message transmission step in which the group management client divides the request and transmits the fragment messages, while the group management server acquires the group information by assembling the fragment messages.
Preferably, the group creation and enrollment step comprises a step in which a multicast application describes session description protocol information by transmitting group information to the group management client, a step in which the group management client performs a group creation process by transmitting a group creation session description protocol to the group management server when the group management client and the group management server exist in the same host, a step in which the group management client enrolls the group in the group management server by compressing or encrypting a session description protocol information on group creation and transmitting the session description protocol information to the group management message by means of a group management protocol message when the group management client and the group management server exist in different hosts, a step in which the group management server transmits a successful group registration response to the group management client by means of a group management protocol message, and a step in which the group management client informs the Internet multicast application of successful group registration.
Preferably, the group query step comprises a step in which the group management client describes a group ID and creates a query session description protocol information for requesting corresponding multicast group information, a step in which the group management client transmits the query session description information to the group management server by means of the group management protocol message, and a step in which the group management server which receives the query session description protocol information announces the group information through a TCP by means of the group management protocol message including a response information.
Preferably, the group registration step comprises a step in which the group management client describes participant enrollment information on an applicant for participation in a certain multicast group in the form of a session description protocol, a step in which the group management client performs a participant enrollment by transmitting the participant enrollment information to the group management server by means of the group management protocol message, and a step in which the group management server informs successful group registration of the applicant by means of the group management protocol message.
Preferably, the group leaving step comprises a step in which the group management client describes group leaving information in the form of a session description protocol, a step in which the group management client requests group leaving by transmitting the group leaving information to the group management server by means of the group management protocol message, and a step in which the group management server which received the group leaving information informs the applicant of successful leaving of the group by means of the group management protocol message.
Preferably, the failure information response step comprises a step in which the group management server describes failure information including error code about a reason of failure in the form of the session description protocol message when the group management server fails in processing the request for group creation, query, enrollment or leaving, and a step in which the group management server transmits the fail ure information to a service requester by means of the group management protocol message.
Preferably, the fragment message transmission step comprises a step in which the group management server describes the group information in the form of a session description protocol, a step in which the group management server divides the session description protocol and creates multiple session announcement protocol fragment messages, and a step in which an applicant for participation who received the session announcement protocol fragment messages assembles the session announcement protocol fragment messages including divided session description protocol information into original session description protocol information and acquires the group information.